Temporary threshold shift of vibratory sensation after clasping a vibrating handle

Summary The temporary threshold shift of vibratory sensation (TTSv) at 125 Hz after clasping a vibrating handle was investigated in relationship to four influencing factors: discrete frequency and acceleration of the vibration exposed to, the grip in clasping a handle and the time after exposure. Clasping the vibrating handle resulted in significantly larger TTSv than shown in clasping a non-vibrating handle. The TTSv after exposure to the 250 Hz vibration was significantly the largest in all frequencies at equal acceleration. The TTSv recovered exponentially as time elapsed after exposure. The TTSv also increased proportionally to the power of acceleration at each frequency and grip force. The larger grip force resulted in a significantly larger TTSv. A general form of regression equation of TTSv involving the four factors was established and its applicability was ascertained by a multiple regression analysis. The prediction equations obtained confirmed that a frequency around 200 Hz induced the largest TTSv among vibrations with equal acceleration and around 240 Hz among vibrations with equal velocity.     

Hearing loss and tinnitus in rock musicians: A Norwegian survey

Our focus in this study was to assess hearing thresholds and the prevalence and characteristics of tinnitus in a large group of rock musicians based in Norway. A further objective was to assess related factors such as exposure, instrument category, and the preventive effect of hearing protection. The study was a cross-sectional survey of rock musicians selected at random from a defined cohort of musicians. A random control group was included for comparison. We recruited 111 active musicians from the Oslo region, and a control group of 40 nonmusicians from the student population at the University of Tromsø. The subjects were investigated using clinical examination, pure tone audiometry, tympanometry, and a questionnaire. We observed a hearing loss in 37.8% of the rock musicians. Significantly poorer hearing thresholds were seen at most pure-tone frequencies in musicians than controls, with the most pronounced threshold shift at 6 kHz. The use of hearing protection, in particular custom-fitted earplugs, has a preventive effect but a minority of rock musicians apply them consistently. The degree of musical performance exposure was inversely related to the degree of hearing loss in our sample. Bass and guitar players had higher hearing thresholds than vocalists. We observed a 20% prevalence of chronic tinnitus but none of the affected musicians had severe tinnitus symptomatology. There was no statistical association between permanent tinnitus and hearing loss in our sample. We observed an increased prevalence of hearing loss and tinnitus in our sample of Norwegian rock musicians but the causal relationship between musical exposure and hearing loss or tinnitus is ambiguous. We recommend the use of hearing protection in rock musicians.     

Dependency of temporary threshold shift of vibratory sensation in fingertip on 1/3 octave-band hand-arm vibration exposure period

Objectives  To investigate the dependency of temporary threshold shift of vibratoty sensation (TTS_v) in fingertip on hand-arm vibration exposure period. Methods  Six healthy students were instructed to grip a vibrating or nonvibrating handle in the experimental room. The gripping force was 40 N. The vibratory sensation threshold at 125 Hz was measured before and after the exposure in the exposed middle fingertip. The exposure vibration was vertical and the 1/3 octave-band vibration with had a central frequency of 200 Hz and an intensity of 39.2 m/s². The exposure periods were 8, 15, 30, 60, 120, 240 and 600 s. TTS_v,t was evaluated as the difference in vibratory sensation threshold between immediately before and t seconds after the exposure. Results  TTS_v recovered exponentially as in several previous studies and its use enabled us to estimate the time constant and TTS_v,0. TTS_v,0 with vibration exposure was significantly larger than that without it. The regression analysis of the relationship between vibration exposure period (T) and TTS_v,0 (T) for each subject confirmed the good fit of the equation TTS_v,0(T)=B₀+B₁ ^*Log₁₀(T), where B₀ and B₁ are the calculated constants (adjusted R²=0.56–0.87). The time constants did not show such a clear dose effect relationship of exposure period as TTS_v,0. Conclusion  The dependency of TTS_v,0 on vibration exposure period was asymptotically proportional to the logarithm of gripping period. To more quantitatively confirm the relationship of the time constants for recovering time course of TTS_v, it may be necessary to improve the measurement method for TTS_v.     

The effect on the temporary threshold shift in hearing acuity from combined exposure to authentic noise and hand-arm vibration

Objectives  

This study examined and compared the effect on temporary threshold shift in hearing (TTS) in healthy subjects of noise and hand-arm vibration (HAV) combined and separately using controlled and authentic exposure conditions. This study also investigated the effect on TTS in hearing in relation to gender after such exposures.     

Application of a new,self-recording,vibratory sensation meter to measure temporary threshold shift of vibratory sensation caused by local vibration exposure

A new, self-recording, vibratory sensation meter measures temporary threshold shifts of vibratory sensation (TTS_v) on a finger tip. After exposure to hand-transmitted vibration with exposure frequencies 63 Hz, 200 Hz and 500 Hz, and levels of acceleration 1 g, 2 g, 4 g and 8 g, fingertip measurements were obtained. Temporary threshold shift immediately after the vibratory exposure (TTSV_v,0) was estimated for each exposure from the regression analysis by approximation of an exponential function. Time constant (t_c) was also estimated at the same time by the analysis. The coefficients of determination were large. Thus, the fit of the exponential function is very good for each exposure. The t_c corresponds to the recovering velocity of the temporary shift and implies the half-life period of TTS_v. These parameters enable us to examine more generally the relationships of TTS_v to the characteristics of exposure vibration, subject and other conditions. On this basis, the estimated TTS_v,0 and t_c were used to examine the dependency of TTS_v on the characteristics of the exposure vibration and the subject. The most effective frequency under the level of 4 g is thought to be between 200 Hz and 500 Hz. TTS_v,0 of each subject proportionally increased with power of acceleration. The coefficient of determination on regression analysis was large. This result enables us to estimate TTS_v,0 at an arbitrary level of acceleration by use of a regression equation derived from experimental data.     

Lung function studies before and after a work shift.

The lung function of 23 underground coal workers and eight surface workers at a Scottish colliery was measured immediately before and after a work shift. Changes in lung function were assessed in relation to the measured respirable dust exposure and the time of day in which the shift was worked. Large, and statistically significant, decrements of lung function during the shift were found in night-shift workers compared with workers on other shifts. Measurements derived from the forced expiratory manoeuvre, particularly FEV1, Vmax50, and Vmax25, after three vital capacity breaths of an 80% He/20% O2 mixture, showed large reductions in night-shift men, smaller reductions in afternoon-shift men, and small increases or decreases in morning-shift underground and surface workers. Within-shift changes for other tests, such as closing volume, N2 index, and volume of isoflow, did not differ significantly between shifts. No significant relationship was found between dust exposure and functional changes during a shift for any test. Lung function changes in a control group of 25 female workers not exposed to dust (hospital nurses) did not show the same large variations between day and night shifts. Examination of a further control group of 16 office workers did not show any difference in diurnal changes between smokers and non-smokers. It is concluded that these coal miners, even on permanent shift patterns, had widely different changes in their lung function cycle depending on which shift they were working. These changes did not appear to be related to dust exposure or cigarette smoking and were not consistent with other biological adaptations known to result from regular night-shift working.     

Soil heavy metal pollution in Ryazan: ecological and hygienic aspects

The paper presents the results of investigations evaluating the soil pollution with heavy metals in Ryazan. The authors have determined the priority pollutants, geochemical anomalies on the territory of the town and the qualitative and qualitative composition of the pollutants in relation to the source of waste and to the specific features of an atmospheric and technogenic transfer. They propose measures to improve the urban ecological and sanitary status, which are associated with the utilization of the plants that accumulate heavy metals and with the replacement of the polluted soil with artificial soil-like masses.